In tuning machines for guitar strings, a string is tensioned by winding one end of the string on a tuning peg fixed to a gear wheel. The gear wheel is driven by a hand-turned worm gear.
In known arrangements, the worm gear is supported by a pair of stamped posts extending from one face of a base plate. Each post has a bore for supporting a shaft of the worm gear. During assembly, a tab extending from the post enters a hole in the base plate to enable the post to be fixed to the base plate by peening over the end of the tab on the side of the base plate opposite from the post. The posts are arranged on the base plate in pairs so a worm gear extending into the bore in each post is supported between a pair of posts.
The worm gear is held in place by a collar placed over one end of a worm gear shaft. The worm gear shaft is on the outer face of a post at a location where the shaft extends through the post. The end of the worm gear shaft is then peened over the collar.
The normal technique for assembling the prior art machine begins by slipping a post over each end of a worm gear and inserting the tabs into a respective hole in the base plate. The machine is then turned over so the posts are pressed against the ends of the worm gear while the tabs are peened over with a hammer or small punch press. The worm gear is then locked in place by slipping a collar over the protruding end of the worm gear shaft and by peening the end of the shaft over the collar.
The peening operations are not conducive to producing a tuning machine that is very true or rigid. Peening the ends of the tabs over tends to deform the bores in the posts, making them more oval than round. Furthermore, the bores which are formed during a stamping operation are not truly round initially. The out of round bores do not properly support the worm gear so that the worm position tends to be sloppy.
The worm gear shaft looseness and effects of end play thereof cause a gear wheel, which is fixed to the spool, to mesh eccentrically with a manually driven worm gear as a result of shifting between them.
An object of the present invention is to provide a new and improved stringed instrument tuning machine having great stability in the position of moving parts and to a method of forming same.
Another object of the invention is to provide a new and improved stringed instrument tuning machine having bores that are drilled and reamed with very high accuracy at predetermined locations in a body of the machine.
A further object of the invention is to provide a guitar string tuning machine that lies flat against wood of the guitar head without forming holes in the head to accept rivets of a base of the tuning machine.
An additional object of the invention is to provide a stringed instrument tuning machine having a button-worm gear assembly that is easily replaced if, for example, it is damaged.
Yet another object of the invention is to provide a stringed instrument tuning machine wherein rotational friction between a manually turned bottom-worm gear assembly and a string winding gear wheel assembly is easily regulated.
Still a further object of the invention is to provide a stringed instrument tuning machine that is easily fabricated enabling a base plate or wall thereof to have a carved, relief design of a type that can not be achieved with prior art stamping methods for forming baseplates.
Yet an additional object of the invention is to provide a stringed instrument tuning machine having increased corrosion resistance.
Still another object of the invention is to provide a stringed instrument tuning machine having a high degree of rotational smoothness between a manually turned button-worm gear assembly and a string winding gear wheel assembly because there is virtually no backlash between the assemblies.